Question

The mass of hydrogen at STP, that is present in a vessel which can hold $4$ grams of oxygen under similar conditions, is:

• A. 1 gm
• B. 0.5 gm
• C. 0.25 gm
• D. 0.125 gm

Answer 1

The correct option is C 0.25 gm

Equal volumes of different gases at STP contains an equal number of moles.

$4$ g oxygen corresponds to $\frac{4}{32}=0.125$ mole. This is also equal to the number of moles of hydrogen. $1$ mole of hydrogen corresponds to $2$ gm.

Hence, $0.125$ mole will correspond to $2\times 0.125=0.25$ gm.

Hence, the correct option is $\text{C}$